Content identifiers triggering corresponding responses

1. A method comprising:

obtaining fingerprint data from a file header associated with a file, the fingerprint data being associated with contents of the file;

checking the integrity of the fingerprint data;

if the check leaves doubt about the fingerprint data thus obtained, then recalculating fingerprint data from contents of the file; and

transmitting the fingerprint data to a database.

2. The method of claim 1 that includes:

accessing a database record corresponding to the transmitted fingerprint data, to obtain associated information; and

returning at least some of said associated information to a computer device from which the fingerprint data was transmitted.

3. The method of claim 1 in which the file contents comprise audio.

4. The method of claim 1 in which checking includes checking a digital signature.

5. The method of claim 1 in which the checking includes decrypting fingerprint data from the header and authenticating the decrypted data.

6. The method of claim 5 that includes applying an inverse modification to the fingerprint in the header prior to said decrypting.

7. The method of claim 1 that includes applying an inverse modification to the fingerprint in the header.

8. A method comprising:

obtaining watermark data from a file header associated with a file, the watermark data being associated with contents of the file;

checking the integrity of the watermark data;

if the check leaves doubt about the watermark data thus obtained, then detecting watermark data from contents of the file; and

transmitting the watermark data to a database.

9. The method of claim 8 that includes:

accessing a database record corresponding to the transmitted watermark data, to obtain associated information; and

returning at least some of said associated information to a computer device from which the watermark data was transmitted.

10. The method of claim 8 in which the file contents comprise audio.

11. The method of claim 8 in which checking includes checking a digital signature.

12. The method of claim 8 in which the checking includes decrypting watermark data from the header and authenticating the decrypted data.

13. The method of claim 12 that includes applying an inverse modification to the watermark in the header prior to said decrypting.

14. The method of claim 12 that includes applying an inverse modification to the watermark in the header.

15. A method comprising:

( a ) obtaining identifier data by reference to first data conveyed with a file;

( b ) if there is cause to doubt the identifier data thereby obtained, then deriving identifier data from contents of the file by application of an algorithm thereto; and

( c ) taking action based on said derived identifier.

16. The method of claim 15 in which act ( a ) comprises:

reading first data conveyed in a header of said file;

by reference to said first data, consulting a remote repository to obtain identifier data corresponding to said first data.

17. The method of claim 15 in which act ( c ) comprises transmitting the derived identifier to a remote database.

18. The method of claim 15 in which act ( b ) comprises authenticating the first data.

19. The method of claim 18 in which said authenticating proceeds with reference to a hash.

20. The method of claim 18 in which the authenticating proceeds with reference to CRC bits.